[from early IBM `Simultaneous Peripheral
Operation On-Line', but is widely thought to be a backronym]
To send files to some device or program (a `spooler') that queues
them up and does something useful with them later. Without
qualification, the spooler is the `print spooler' controlling
output of jobs to a printer; but the term has been used in
connection with other peripherals (especially plotters and graphics
devices) and occasionally even for input devices. See also
demon.